As a floating construction such as a carrier vessel or an ocean floating facility for carrying or storing liquid cargos such as petroleum, LPG (liquefied petroleum gas), and LNG (liquefied natural gas), a floating construction of an independent tank system is widely used in which tanks for storing the liquid cargos are set independently from the floating construction (see, for example, Patent Literature 1 and Patent Literature 2). When liquefied gas (e.g., LNG) is used as a propellant for ships such as a container ship, an oil tanker, a general cargo ship, and a passenger ship, it is planned to adopt the independent tank system in which a liquefied gas fuel tank is set independently from the hull as in the case of the liquid cargo.
In the floating construction during a voyage or during an anchorage, motions are caused by the influence of the waves; heaving in which the floating construction linearly shakes up and down, swaying in which the floating construction linearly shakes to the left and the right, surging in which the floating construction linearly shakes to the front and the back, pitching in which the head and the tail of the floating construction linearly vibrate up and down around the center, yawing in which the head and the tail of the floating construction vibrate to the left and the right around the center, and rolling in which the sides of the floating construction vibrate up and down with the center as an axis. Actually, complicated motions in which these motions are entangled occur. Therefore, in a tank of the independent tank system relatively movable to the floating construction, it is important to stably support the tank.
For example, in FIG. 5 and FIG. 6 of Patent Literature 1, a structure is disclosed that supports a tank with a bearing sheet, a floating chock (an anti-floatation chock), and a rolling chock (an anti-rolling chock). The bearing sheet is a support structure that supports a vertical load of the tank. The rolling chock (the anti-rolling chock) is a support structure that supports a horizontal load in the case in which the tank shakes in the lateral direction because of rolling of a hull. The floating chock (the anti-floatation chock) is a support structure that suppresses a lift of the tank during submersion. Therefore, the deadweight of the floating construction and loads of the motions of the floating construction caused by the influence of the waves are mainly supported by the bearing sheet and the rolling chock (the anti-rolling chock). As described in Patent Literature 1, the bearing sheet is arranged in the bottom section of the hull and the rolling chock (the anti-rolling chock) is arranged in the ceiling section and the bottom section of the hull.
In FIG. 14 and FIG. 15 of Patent Literature 2, a support structure is disclosed including a base support that supports a base of a tank for supporting the weight of the tank, a tank support surface provided on the tank, and a hold support surface provided on a hold and configured to cooperate with the tank support surface. The support surfaces extend toward a direction of heat transfer of the tank and extend at an intermediate angle between the horizontal direction and the vertical direction to suppress the movement in the lateral direction of the tank with respect to the hold. Note that the tank support surface and the hold support surface cooperating with each other extend toward a direction to the center of the base of the tank along the direction of the heat transfer.